*ahem* If you would all be so kind as to get back on topic, I would like to discuss whether the Empire intervening in Skyrim's rite of succession was justified considering the circumstances, or if the Stormcloaks are right in accusing the Empire of corrupting Nord politics and infringing on their traditions.
If the Imperials had just let (made) the Nords hold a moot after Ulfric killed Torygg, instead of branding Ulfric a murderer and chasing him out of town, things would have been a lot better. They would have had a vote, Ulfric would have won or lost. If he won, then so be it, the Nords have the right to vote for their high king and the Imperials have no business interfering with that.
If he had lost and started his civil war (or if Ulfric had refused to participate in the moot and started his civil war), then Ulfric could have been branded an outlaw for not following Nord custom.
The biggest mistake the Imperials made was chasing Ulfric out of town and preventing a moot. That was percieved as trampling on Nord customs and served to galvonize "true Nords" behind Ulfric.
The Imperials must have thought Ulfric would have won the moot, but the outcome was far from clear since so many Jarls across Skyrim have Imperials coin in their pockets. Even Balgruuf does not support Ulfric. The Imperials should have just followed Nord law and held a moot. I don't see how the Imperials were "justified" in preventing Skyrim from following the lawful Nord process for selecting a new leader.